A case-control study of risk factors for sporadic hepatitis C virus infection in the southwestern United States.

We performed a case-control study to evaluate risk factors and possible modes of transmission for hepatitis C virus (HCV) infection in patients with no history of blood transfusion or injection drug use. Study subjects were selected from among patients seen in gastroenterology outpatient clinics at a university medical center in the southwestern United States. The study group consisted of 58 patients (12%) with chronic HCV infection who reported no history of transfusion or injection drug use, among a total of 477 patients evaluated for a positive HCV antibody test. These 58 patients were matched by age, ethnicity, and gender with 58 control patients diagnosed with gastroesophageal reflux attending the same clinics. Patients and controls were subjected to structured interviews and review of medical records. A variety of variables were significantly associated with increased risk of sporadic HCV infection, including a history of tattoos, needlestick exposure, a history of sexually transmitted disease, intercourse with an injection drug user, five or more lifetime sexual partners, intercourse during menses (for women), lower income, and heavy alcohol intake (>60 g/day). Multivariate analysis identified a history of sexually transmitted disease, heavy alcohol intake, and the presence of a tattoo as independent risk factors for sporadic HCV. In addition, six cases and one control had a history of needlestick exposure. Of the cases, 88% had at least one of these four risk factors, as compared with 26% of controls (odds ratio = 16.5; 95% confidence interval = 4.0-68.8). A history of sexually transmitted disease, heavy alcohol intake, the presence of tattoos, and a history of needlestick exposure were identified as risk factors for sporadic hepatitis C in this case-control study. If we include all patients with a history of blood transfusion or injection drug use, only 2% of the total 477 HCV patients had no identified risk factors.